1. Field of the Invention
The present invention relates to an inhaler for ejecting medicine, aromas, nicotine, etc., in the form of droplets so that the user can inhale the droplets.
2. Description of the Related Art
With recent advances in medicine and science, the average life expectancy has increased and society is becoming more elderly as a whole. On the other hand, however, new diseases and infections due to changes in dietary life and living environments, environmental pollution, and viruses and fungi have been found. This increases people's anxiety about health. In particular, in countries referred to as developed countries, it is important to cope with increases in the number of patients with lifestyle diseases, such as diabetes and hypertension, and to improve cures for such diseases.
For example, since insulin is not secreted in diabetics, particularly, Type I insulin-dependent diabetics, it is necessary for diabetics periodically to inject themselves with insulin. While insulin is currently injected by hypodermic injection, this imposes heavy physical and mental burdens on the diabetics. In order to reduce the burdens on the patient, a pen-shaped syringe that has a thin needle so as to cause little pain to the patient has been developed. However, Type I diabetics frequently live lifestyles similar to those of healthy persons except for the necessary periodical insulin injections. Therefore, even when the syringe is pen-shaped, the diabetic patient may be mentally hesitant to take an insulin shot in public, and therefore, it may be difficult to take insulin shots at appropriate times. As a result, this method may hinder proper procedures for diabetic sufferers.
As another solution, a method in which the user inhales medicine with an inhaler has been developed. In this method for administering medicine through the respiratory system, the user does not feel any pain, unlike when using a syringe. For example, International Publications Nos. WO95/01137 and WO02/04043 disclose inhalers in which the principle of an inkjet method is applied to ejection.
When such inhalers are used, it is necessary accurately to manage the dosage and dose interval of medicine according to the relevant prescriptions, and efficiently to apply the medicine under proper ejection control. For example, the diameter of droplets of medicine at a suction port (the portion to be held in the user's mouth to inhale the medicine) of an inhaler has an influence on the probability that the medicine will reach the alveoli. For this reason, it is preferable that the inhaler provide droplets having a fixed diameter, regardless of the use condition thereof. Unfortunately, the user does not always use the same ejection unit, according to the phase of treatment. While the diameter and ejection frequency of medicine droplets to be ejected have an effect on the amount of moisture evaporation from the droplets during their flight from the inhaler into the patient's body, they may vary according to the ejection unit being used. In other words, even when the inhaler is used in the same environment every time, the diameter of droplets at the suction port may change according to the use condition of the inhaler. This hinders consistent inhalation of the proper dosage prescribed by the doctor. International Publication No. WO1996/009846 discloses an inhaler in which evaporation is promoted with a heater and a dehumidifier so as to obtain droplets having a fixed diameter. As another method for promoting evaporation, International Publication No. WO00/24362 discloses an inhaler in which a passage of a mouthpiece is extended.
Type I diabetics who rely on inhalers must always carry the inhalers, because of the necessity for the periodic administration of medicine. Therefore, there is a demand for a small and lightweight inhaler that allows a user to inhale droplets having a fixed diameter, regardless of the use condition.
However, in the inhaler described in International Publication No. WO1996/009846, a heater and a dehumidifier are necessary as generating devices that generate gas for promoting evaporation. When all the energy necessary for driving the inhaler is to be provided from a source in the inhaler, in consideration of portability, the need to sufficient an energy to drive the generating devices can result in a structure that increases the size and weight of the inhaler.
International Publication No. WO00/24362 does not specify a variable that serves as a basis of control of the length of the passage in the mouthpiece. As a result of this, also, the size and weight of the inhaler may be increased.